Flash evaporator



Nov. 22, 1949 c. J. LocKMAN FLASH EVAPORATOR Filed Oct. 3l, 1945Patented Nov. 22, 1949 FLASH EVAPORATOR Carl Johan Lockman, Enebyberg,Sweden, as-

signor to Aktiebolaget Rosenblads Patenter,

Stockholm, Sweden Application October 31, 1945-, Serial No. 625,783 InSweden September 20, 1943 The present invention refers to evaporatingapparatus and more particularly to such apparatus as the ash evaporatingtype working with circulation of the liquor to be evaporated through aheat exchanger and a ash chamber, and in which the heat exchanger is sooperated for cleaning purposes that the liquor and a heating medium arepassed alternately through changed channel systems.

In this kind of apparatus it is important that the change of the liquorstream from one to the other channel system of the heat exchanger doesnot cause any loss f the liquor body which is contained in theliquor-conducting channel system 'before the change but that all theliquor should be carried in circulation also after. the change and thatthis should be'secured by suitable measures for the change.

With this in viewfit is the chief object of the invention to providearrangements whereby it is rendered possible to force the liquorremainingin one or the other channel system of the heat exchanger when achange is desired to be passed back towards the flash chamber the sameway as previously entered therefrom so that also this liquor body maythen be included in the circulating flow through the changed channelsystem.

By way of example one embodiment of an apparatus according to theinvention is illustrated in the accompanying drawing which more or lessdiagrammatically shows a side view of such apparatus.

In the drawing I is a flash chamber and 2 a heat exchanger of the platetype comprising two separate channel systems 2a and 2b with inor outletpipes a and aa, b and bb, respectively. Further, there is providedsupply means for liquor as by the pipe 3 and its branches 3a and 3b withvalves a3 and b3, respectively, which are connected with the bottom endsof the channel systems 2a and 2b, respectively, over inor outlet pipes aand bb, respectively. Similarly the 2 Claims. (Cl. 159-22) top ends ofthe channel systems are connected through in'- or outlet pipes aa and bwith discharge means for liquor as by valves a4 and b4, respectively, inbranches 4a and 4b, respectively, of pipe 4. On the other hand theliquor supvply and discharge pipes 3 and 4, respectively, are connectedwith' the flash chamber I so as to form a circulating path for theliquor which may thus be passed. from the flash chamber through pipe 3and either of its branches 3a or 3b through channel system 2a or 2b,respec- 2 pipe 4a or 4b, respectively, and pipe 4 back to the flashchamber again. Likewise heating steam may be fed to any one of thechannel systems by means of a corresponding supply and discharge systemcomprising pipe 5 with branches 5a and 5b and valves a5 and b5,respectively, for supplying steam to the top inor outlet pipes aa or b,respectively, of channel sysstems 2a and 2b, respectively, as desired,and branches 6a and 6b with valves a6 and h6, respectively, of pipe 6 inconnection with the bottom inor o utlet pipes a and bb, respectively,for discharging condensate from channel sysstem 2a or 2b as the case maybe. In addition there is a pipe 1 with a shut-off valve 'Iv Y connectedwith the steam supply pipe 5 between a shut-off valve 5v in that pipeand the branch' pipe valves in order to admit the introduction ofcompressed air or gas and the like in the channel systems'of the heatexchanger, if desired.

Now, as indicated in the drawing by arrows it is assumed that the liquorto be evaporated circulates from the flash chamber through pipe 3 andbranch 3a, valve a3 being open and valve b3 being closed, and thencethrough pipe a to the channel system 2a in heat exchange Valve a6 beingclosed. From channel system 2a the liquor flows through pipe aa andbranch 4a, valve a4 being open and valve a5 being closed, and thencethrough pipe 4 back to the the evaporator, valve b4 being closed. At the,same time steam is fed through pipe 5 and the open branch 5b to thechannel system 2b in the heat exchanger, from which channel system thecondensate is discharged through the open branch 6b and pipe 6. Thus, inthe heat exchanger the liquor is heated by heat transmission from thesteam and this occurs under higher pressure than prevails in the flashchamber, and therein the pressure is relieved so that eva-poration ofthe liquor will take place, the vapours escaping to .the top to bewithdrawn by a discharge pipe therefrom and the liquor forming a pool inthe bottom space from which it is circulated again.

When it is desired to effect interchange of4 media between the channelsystems this may conveniently be carried out in the following manner.First valve b5 is closed to shut oil the steam supply to the channelsystem 2b. Valve a5 is opened in order to direct the steam to thechannel system 2a and valve a4 is closed to prevent the steam flowingdirectly to the evaporatoi` I. Since the steam ofcourse has a somewhathigherV pressure than the liquor in that channel,

tively, as desired, and through either branch the steam tends to forcethe liquor out of the /ing body as desired, the invention eens for anarrangement which includes a suitable positioning of the heat exchangerrelative the flash chamber whereby such a relation between thecounteracting pressures referred` to is estab- 1. In an evaporatingsystem, a surface heat exchanger having a wall separating twofiuidpassages in heat exchange relation with each other. .a flashchamber disposed at a higher elevation .than said heat exchanger, afirst conduit connected to said ash chamber, branch conduits connectingsaid first conduit'with one end of each of said passages, a secondconduit connected i to said iiash chamber, branch conduits connectlishedso that the liquor level will be caused to fall below the liquorin-let'to the channel system 2a. Generally, the heat exchanger should bepositioned at the lowest suitable level so that circulation isfacilitated as much-as possible.

However, sometimes local conditions or other considerations may' notallow such positioning of the heat exchanger-as proposed and in thatcase,

there may be needed a medium of higher pressure than the heating steamto displace the liquor from the respective 'channel system in the mannerdescribed. To this end the invention provides. for introduction ofcompressed air, gas or thelike of suitable pressure into the channelsystem through pipe 'I by opening valve 1v, after closing valve 5v, fordisplacing the liquor before the heating steam is admitted to samechannel system. Y

After the liquor in the channel system 2a has been displaced by theheating steam, valve a3 is manner described', the heat exchanger willbe' kept practically clean while in uninterrupted operation andcontinually maintained at very high eiliciency.L i l It is understoodthat various changes may be made in the apparatus shown and methodsdescribed without deviating from thel scope of the invention which isnot limited otherwise than by the appended claims. l What I claim anddesire to secure by Letters Patent is: y

ing said second conduit with the opposite end of `each of said passages,a third conduit for supplying-a heated iluid medium under pressure,branch conduits connecting said third conduit to said opposite end ofeach of said passages, a fourth conduit for discharging cooled heatingmedium, branch conduits connecting said fourth conduit ,to said one endof each of said passages, and a valve disposed in each of the aforesaidbranch conduits and operable to permit flow of fluid from said flashchamber through either of said passages and back to said chamber whilepermitting flow of heating medium from said third conduit through theother of said passages and to said fourth conduit, said valves alsobeing operable to permit owof fluid under pressure from said thirdconduit into the opposite end of the same passage whichis connected tosaid ilash chamber by said first conduit, whereby fluid is forced backfrom said same passage to the higher elevation in said flash chamber.

2. An evaporating system as defined in claim 1 including a fth conduitfor supplying a gas under pressure, and a valved connection between saidfourth and fth conduits whereby the pressure of said gas is utilized toforce the fluid back from said same passage to the higher elevation insaid flash chamber.

CARL JOHAN LOCKMAN.

i REFERENCES CITED,

The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,006,197 Frasch Oct. 17, 19111,819,517 Lichtenthaeler Aug. 18, 1931 1,997,980 Smith Apr. 16, 1935FOREIGN PATENTS Number Country Date 363,116 Great Britain Dec. 4, 1930

